/* 定义常用属性变量 */
:root {
  --prime-color: #13227a;
  --prime-1: #e8efff;
  --prime-2: #adbde4;
  --prime-3: #7b8fca;
  --prime-4: #5065af;
  --prime-5: #2e4095;
  --prime-6: #13227a;
  --prime-7: #0d186f;
  --prime-8: #080f63;
  --prime-9: #030858;
  --prime-10: #00014d;
}

body {
  width: 780px;
  margin: 0 auto;
}
p {
  font-size: 18px;
  /* text-indent: 2em; */
  text-align: justify;
  line-height: 2;
}
h1 {
  color: var(--prime-color);
}
pre {
  font-family: "Noto Serif SC";
  font-weight: 700;
  font-size: 18px;
  line-height: 2;
  color: hsl(0, 0%, 18%);
  letter-spacing: 1px;
}

h2 {
  /* text-decoration: underline; */
  background-image: url(img/school.svg);
  background-repeat: no-repeat;
  background-size: 32px;
  padding-left: 42px;
  color: var(--prime-color);
  margin: 80px auto 40px;
}

img {
  display: block;
  width: 90%;
  margin: 0 auto;
}

/* 视频播放器样式 */

#vs {
  width: 90%;
  margin: 64px auto;
}

/* 摘要样式 */

.abstract {
  background-color: rgb(215, 215, 215);
  background: linear-gradient(#f5f5f5, #d7d7d7);
  padding: 1em;
  margin: 40px auto;
  border: 1px solid var(--prime-2);
  border-radius: 4px 16px;
}
.abstract p {
  font-size: 13px;
  line-height: 2;
}

/* 页脚区域 */
.extra {
  background-image: url("img/bg-demo.jpg");
  color: white;
}
